Indwelling ureteral catheter stents or drainage tubes have been used to bypass ureteral obstructions or uretero-vaginal fistulas and maintain urinary drainage. In the past, stents made of straight lengths of open end tubing have been used for this purpose and have provided good drainage for sustained periods of time. However, the use of such open end tubing has not been completely satisfactory. For example, in some instances, the tubing has migrated and in others it has been expelled.
Various attempts have been made to produce stents which do not have the problems which accompany the use of such tubing. For example, stents have been designed which are closed at one end to facilitate passage into a body passage and which have at the other end a flange to make upward migration of the stent less likely. Another approach has been to provide the body of the stent with sharply pointed barbs which are designed to prevent downward migration and expulsion. However, such barbs increase the diameter of the stent making it more difficult to insert and in some instances can cause the stent to migrate outside the bladder.
In U.S. Pat. No. 4,212,304 issued July 15, 1979 and U.S. Pat. No. 4,307,723 issued Dec. 29, 1981, ureteral stents are disclosed which have hooks at each end which are surprisingly effective in preventing migration and expulsion. The patented stents are widely accepted because they can be easily introduced both endoscopically and during open surgery.
All the commercially available stents have several disadvantages in common. If they are soft and flexible enough to not cause patient discomfort it is difficult to maneuver them past obstructions in the ureter and if they must be removed they are difficult to replace.